To connect structures such as a hollow shaft or a pipe having a doughnut shape and inner and outer diameters, a separate connecting bracket, which surrounds an outer portion of the structure or is inserted into an inner portion of the structure, is necessarily required.
However, in the related art, the connecting bracket generally needs to necessarily coincide with the outer or inner diameter, and as a result, there is a problem in that the connecting brackets, which correspond to varying diameters, are required.
In addition, products such as shaft pins, which are fastened in an interference fit manner, also need to be installed after being manufactured to have a size corresponding to the diameter, and as a result, it is difficult to manufacture the product.